Abstarct: Olang coal mines are located 100-130 km to the south of Gorgan and 20 km from Ramian, in Ghareh Chay catchment. In this study, the environmental effects of mining in this area including slope instability, surface water pollution (including microbiological pollutants) and erosion problems have been evaluated. To undertake this research, all slides were mapped and the probable causes assessed. The result of the study show that the frequency of slides in mining area is more than the other locations and the human activity together with the suitable natural conditions such as geology, climate, hydrology have led to instability. For the assessment of surface water pollution, 34 samples were taken from the drainage lines, upstream and downstream of mining tunnels. The results of water quality tests show that the mine drainage increases salinity and organic content of surface waters, but do not significantly change the concentration of heavy mextal.